1. Field of the Invention
The present invention relates to chemical-mechanical polishing, and more particularly using elimination solution to improve a multi-step chemical-mechanical polishing method during the chemical-mechanical polishing is operating.
2. Description of the Prior Art
Chemical-mechanical polishing (CMP) is conventionally used in semiconductor manufacturing to achieve global planarity, usually with planarity greater than 94%. Normally the operation of the chemical-mechanical polishing combines both of chemical and mechanical effects. The chemical-mechanical polishing generally includes rotating table, where slurry and polishing pad are applied. Conventionally typical polishing slurry comprises SiO.sub.2, alumna Al.sub.2 O.sub.3 in an alkali solution.
There generally will be many particles existing on the surface of wafer after tungsten chemical-mechanical polishing WCMP process. All particles usually distribute onto the surface edge of wafer. Due to the inherent drawbacks of the chemical-mechanical polishing mechanism, the slurry effect is clearly observed after the chemical-mechanical polishing, causing serious alkali or acid solution effect including SiO.sub.2 and Al.sub.2 O.sub.3 slurry, which disadvantageously affects following manufacturing process. Normally solution effect will appear obviously if oxide wafer with oxide slurry buffing process is carried out. However, particles would not exist on tungsten wafer with oxide slurry buffing process. Due to the pH rate of tungsten slurry is about 2.3 and the pH rate of oxide slurry is about 11. Probably the neutralization of chemical reaction happens leading to the special morphologic particles existed as FIG. 1A. And FIG. 1B shows for its close-up dramatic picture.
According to the foregoing reasons, a method is exactly needed for eliminating the solution effect during the chemical-mechanical polishing in order to improve and reduce either alkali or acid solution effecting the result of polishing process.